Method for the chemical treatment, like cleaning or pickling, of installations with at least one steam generator

ABSTRACT

Method for the chemical treatment of a steam generator system. Chemical system treating materials are introduced into the evaporation portion of the steam generator and circulation is induced therein by the injecting of a gas, including air, thereinto. Chemical materials then exiting from the evaporation portion of the steam generator are driven by a pump through the remainder of the system.

United States Patent [191 Dahm [451 May 27, 1975 METHOD FOR THE CHEMICAL TREATMENT, LIKE CLEANING OR PICKLING, OF INSTALLATIONS WITH AT LEAST ONE STEAM GENERATOR [75] Inventor: Victor Dahm,Winterthur,

Switzerland [73] Assignee: Beratherm AG, Zurich, Switzerland [22] Filed: Oct. 19, 1973 [21] Appl. No.: 408,199

[52] U.S. Cl 134/3; 122/379; 134/22 C; 134/30; 134/102 [51] Int. Cl B081) 9/06; C23g H02 [58] Field of Search 134/37, 34, 30, 22 C, 22 R, 134/10, 99, 102, 3, 36; 122/379 [56] References Cited UNITED STATES PATENTS 9/1938 Butzler 134/34 UX 2,222,516 11/1940 Powell et a1. 134/37 UX 2,510,701 6/1950 Cross 134/37 UX 2,818,076 12/1957 Erling 134/37 UX Primary Examiner-S. Leon Bashore Assistant Examiner-Richard V. Fisher Attorney, Agent, or Firm-Woodhams, Blanchard and Flynn [5 7] ABSTRACT Method for the chemical treatment of a steam generator system. Chemical system treating materials are introduced into the evaporation portion of the steam generator and circulation is induced therein by the injecting of a gas, including air, thereinto. Chemical materials then exiting from the evaporation portion of the steam generator are driven by a pump through the remainder of the system.

9 Claims, 1 Drawing Figure METHOD FOR THE CHEMICAL TREATMENT, LIKE CLEANING OR PICKLING, OF INSTALLATIONS WITH AT LEAST ONE STEAM GENERATOR It is known in the chemical treatment of once through forced flow steam generator installations to add the necessary chemicals to the flow of liquid of a feed water pump at a point downstream from said pump, which liquid then flows through the steam generator. The liquid is drained off after it has flowed through the pipes, which must be treated, of the complete system, including water cycle, steam cycle, economizer, evaporator, superheater, collector and container, steam lines and reheater. Particularly, such liquid can be then discharged into a neutralizing basin so that pipeline parts and machine parts which are not to be exposed to this cleaning process are not exposed to the chemicals. It is possible to expel initial portions of the cleaning solution, which portions are heavily loaded with dissolved particles, at various intermediate points prior to same entering the next part to be treated.

In steam generators with a liquid circulation which is effected by differences in the specific weight of the liquid, that is so-called natural circulation steam generators, an autocirculation which is produced by injecting a gas, such as air or other gases into the pipe system of the steam generator, which pipe system is filled with water or treatment solution, has proven to be advantageous for the treatment of such steam generators or other apparatuses based on the thermosyphon system.

The invention relates to a method for the chemical treatment, cleaning or pickling of installations of the type having at least one steam generator with primarily an approximately vertically directed circulation and also having at least one pipe system connected thereto. The latter may include, for example, supplemental heating surfaces like an economizer, superheater and reheaters. According to the inventive method, in the said steam generator a self-circulation (autocirculation) is effected by injecting air or gas in a lower zone of this steam generator and in the pipe system a forced flow, for example by a pump, is utilized.

The objective of the invention is the combination of the autocirculation method for the evaporator part with the forced circulation method for the remaining elements which are to be cleaned.

The operation will be discussed in connection with the drawing which illustrates an example thereof. The feed-water pump 2 conveys water from the feed-water tank 1 and leads same first to the economizer 3 and then to the steam generator 4. At the same time the proportioning pump 6 conveys chemicals, for example HCl or HF, from the mixing container and leads same l 7, through a bypass 8 of the turbine 12a, through the to the treatment through flow path at a point between the pump 2 and the economizer 3. The steam generator 4, which at first is empty, is slowly filled by the treatment liquid (the mentioned water and chemicals). For the purpose of circulating the liquid in the evaporator section of the steam generator, a gas (e.g. air or other gases) is guided to various points 11 therein in such a manner that approximately the same circulation speed is created in the entire conduit, or pipe, system of the evaporator section. When the steam generator is full, same then overflows through a pipe 4A and the treatment liquid in pipe 4A is urged through the superheater reheater 9 and through the steam pipe up to a point 20 ahead of the turbine 12b, after which the liquid is discharged through the outlet 10A or if necessary is guided into a neutralizing tank 10. superheater 7 and reheater 9 each include a system of parallel pipelines. According to the invention the pipe system of the superheater and reheater, evenly distributed over all pipelines, receives additionally or independently from the chemicals which have already been fed to the steam generator, the same or further chemicals which can with reference to type and concentration correspond to the, if desired, different material of the pipes and the specific contamination of the economizer, steam generator, superheater and reheater. For example, the drawing shows at 21 a line for force supplying chemicals from the proportioning pump 6 to the pipe system of the superheater 7. The treatment liquid solution which goes from the steam generator 4 into the superheater 7 may be checked prior to exiting from the steam generator and, if desired, may be discharged directly through a discharge line 13 until a clean solution there appears.

In particular this partially or entirely independent proportioning of the chemicals is especially important in the case of the hydrofluoric acid. Hydrofluoric acid is advantageously applied as a treatment liquid in a weak concentration, for example 1%, and its concentration is further decreased after circulating within the steam generator due to the presence in the hydrofluoric acid treatment solution of the released particles of pipe coating materials from the steam generator. Thus, the concentration of the treatment liquid applied to the superheater 7 may be returned to the correct value by the additional supply of chemical through line 21.

The combination of the through-flow system with the autocirculation method has the advantage that those parts which through their shape are suitable for an autocirculation can be treated according to the economical autocirculation system without requiring that completely separate treatments must be carried out for the various parts to be treated. The combination thus means a substantial savings in time and expense.

A further improvement of the combined treatment in the through-flow and in autocirculation, consists in that a change-over valve 22 is installed temporarily ahead of the steam generator with which, during the autocirculation, the steam generator can be completely switched off from the through-flow, while the steam generator, at most after a chemical exhaustion of the treatment solution in the steam generator, can be switched on into throughflow again temporarily.

Although a particular preferred embodiment of the invention has been disclosed above for illustrative purposes, it will be understood that variations or modifications thereof which lie within the scope of the appended claims are fully contemplated.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method for chemically treating, including cleaning, pickling and the like, of installations of the type having at least one steam generator, wherein the steam generator is of the natural circulation kind having substantially vertically directed circulation conduits and operable on the thermo-syphon principle during steam generation, said installation being further of the type having a forced through-flow system to which the steam generator is connectible at an intermediate point wherein a first part of said through-flow system is preceded by a feed-water pump and is located ahead of said steam generator in series with the remaining part of said through-flow system which follows said steam generator, said through-flow system parts including at least one parallel pipe system, said method comprising the steps of:

first introducing a treatment liquid into said part of said installation in front of said steam generator and urging said treatment liquid through said part with said pump and filling said steam generator with said treatment liquid from said first part;

injecting a gas into the treatment liquid in the lower zone of the steam generator and thereby reducing the specific weight of such treatment liquid thereat to effect a self-circulation of the treatment liquid within the steam generator;

subsequent to complete filling of the steam generator, forcing a flow with said pump of treatment liquid from the steam generator through the following part of said through flow system;

whereby treatment liquid self-circulates within the steam generator for chemical treatment of the conduits thereof and treatment liquid is forcibly circulated by said pump through the pipe systems of the prior and following parts of the through-flow systern.

2. A method according to claim 1 including the step of forcing with a proportioning pump a flow of treatment chemical into mixing contact with feed-water exiting from said feed-water pump and thereby forming said treatment liquid in the through-flow system ahead of said steam generator and the first of said pipe systems to be treated.

3. A method according to claim 2 including the further step of forcibly supplying additional treatment chemical to said through-flow system immediately following said steam generator so as to change the concentration of the treatment liquid beyond said steam generator and preceding the piping systems in said remaining part of said through-flow system.

4. A method according to claim 2 in which said part of said through-flow system following said steam generator includes several pipe systems having parallel pipelines therein and including the further step of pumping treatment chemical to the through-flow system between the steam generator and the first of said parallel pipelines following same and thereby modifying the concentration of chemical in the treatment liquid pumped from the steam generator to said first of said parallel pipelines at least to compensate for changes in concentration. due to self-circulation within said steam generator, of portions of the treatment liquid overflowing therefrom into the pump-forced flow to said first of said parallel pipelines.

.5. A method according to claim 1 in which said step of injecting a gas includes guiding of the gas to points located on the conduits of the evaporator section of the steam generator and selected such that approximately the same speed of circulation of treatment liquid is created in the entire conduit system of the steam generator evaporator section.

6. A method according to claim 1 including the step of checking the concentration of the treatment liquid solution overflowing from the steam generator toward the following portion of said throughflow system and bypassing same away from said following part of said through-flow system to a discharge line until such overflow is clean and only thereafter permitting treatment liquid from within said steam generator to pass to the following part of said through-flow system.

7. A method according to claim 1 in which said part of said through-flow system between said pump means and steam generator comprises an economizer, wherein said economizer includes one of said piping systems, the portion of said through-flow system following said steam generator including, in series a superheater and reheater and treatment liquid outlet, wherein said superheater and reheater include further ones of said pipe systems, and wherein the step of force flowing of treatment liquid through said through-flow system includes urging the treatment liquid with said feedwater pump, serially through the pipe systems of said economizer, superheater, reheater and outlet.

8. A method according to claim 7 in which the treatment liquid is weakly concentrated hydrofluoric acid and including the step of injecting additional solvent into the said through-flow system between said steam generator and said following part of said through-flow system to compensate for lessening of the concentration of said treatment liquid portion which has overflowed from the steam generator after treatment thereof and also to accord with the type of materials used in the superheater and reheater and the expected level of contamination in the piping therein.

9. A method according to claim 8 including after completion of filling of said steam generator with treatment liquid and during treatment of the conduits therein by self-circulation of the treatment liquid therewithin, the further step of feeding of the treatment liquid from the economizer connected ahead of the steam generator directly to the superheater connected after the steam generator with said pump means while isolating said steam generator from said through-flow system, and including the subsequent step of renewing the treatment liquid in the steam generator by temporarily connecting same into through-flow system, wherein further treatment liquid from the pump and economizer is supplied to the steam generator and existing treatment liquid in the steam generator overflows to the following part of said through-flow system including said superheater. 

1. A METHOD FOR CHEMICALLY TRATING, INCLUDING CLEANING, PICKLING AND THE LIKE, OF INSTALLATIONS OF THE TYPE HAVING AT LEAST ONE STEAM GENERATOR, WHEREIN THE STEAM GENERATOR IS OF THE NATURAL CIRCULATION KIND HAVING SUBSTANTIALLY VERTICALLY DIRECTED CIRCULATION CONDUITS AND OPERABLE ON THE THERMOSYPHON PRINCIPLE DURING STEAM GENERATION, SAID INSTALLATION BEING FURTHER OF THE TYPE HAVING A FORCED THROUGH-FLOW SYSTEM TO WHICH THE STEAM GENERATOR IS CONNECTIBLE AT AN INTERMEDIATE POINT WHEREIN A FIRST PART OF SAID THROUGH-FLOW SYSTEM IS PRECEDED BY A FEED-WATER PUMP AND IS LOCATED AHEAD OF SAID STEAM GENERATOR IN SERIES WITH THE REMAINING PART OF SAID THROUGH-FLOW SYSTEM WHICH FOLLOWS SAID STEAM GENERATOR, SAID THROUGH-FLOW SYSTEM PARTS INCLUDING AT LEAST ONE PARALLEL PIPE SYSTEM, SAID METHOD COMPRISING THE STEPS OF: FIRST INTRODUCING A TREATMENT LIQUID INTO SAID PART OF SAID INSTALLATION IN FORNT OF SAID STEAM GENERATOR AND URGING SAID TREATMENT LIQUID THROUGH SAID PART WITH SAID PUMP AND FILLING SAID STEAM GENERATOR WITH SAID TREATMENT LIQUID FROM SAID FIRST PART;
 2. A method according to claim 1 including the step of forcing with a proportioning pump a flow of treatment chemical into mixing contact with feed-water exiting from said feed-water pump and thereby forming said treatment liquid in the through-flow system ahead of said steam generator and the first of said pipe systems to be treated.
 3. A method according to claim 2 including the further step of forcibly supplying additional treatment chemical to said through-flow system immediately following said steam generator so as to change the concentration of the treatment liquid beyond said steam generator and preceding the piping systems in said remaining part of said through-flow system.
 4. A method according to claim 2 in which said part of said through-flow system following said steam generator includes several pipe systems having parallel pipelines therein and including the further step of pumping treatment chemical to the through-flow system between the steam generator and the first of said parallel pipelines following same and thereby modifying the concentration of chemical in the treatment liquid pumped from the steam generator to said first of said parallel pipelines at least to compensate for changes in concentration, due to self-circulation within said steam generator, of portions of the treatment liquid overflowing therefrom into the pump-forced flow to said first of said parallel pipelines.
 5. A method according to claim 1 in which said step of injecting a gas includes guiding of the gas to points located on the conduits of the evaporator section of the steam generator and selected such that approximately the same speed of circulation of treatment liquid is created in the entire conduit system of the steam generator evaporator section.
 6. A method according to claim 1 including the step of checking the concentration of the treatment liquid solution overflowing from the steam generator toward the following portion of said throughflow system and bypassing same away from said following part of said through-flow system to a discharge line until such overflow is clean and only thereafter permitting treatment liquid from within said steam generator to pass to the following part of said through-flow system.
 7. A method according to claim 1 in which said part of said through-flow system between said pump means and steam generator comprises an economizer, wherein said economizer includes one of said piping systems, the portion of said through-flow system following said steam generator including, in series a superheater and reheater and treatment liquid outlet, wherein said superheater and reheater include further ones of said pipe systems, and wherein the step of force flowing of treatment liquid through said through-flow system includes urging the treatment liquid with said feedWater pump, serially through the pipe systems of said economizer, superheater, reheater and outlet.
 8. A method according to claim 7 in which the treatment liquid is weakly concentrated hydrofluoric acid and including the step of injecting additional solvent into the said through-flow system between said steam generator and said following part of said through-flow system to compensate for lessening of the concentration of said treatment liquid portion which has overflowed from the steam generator after treatment thereof and also to accord with the type of materials used in the superheater and reheater and the expected level of contamination in the piping therein.
 9. A method according to claim 8 including after completion of filling of said steam generator with treatment liquid and during treatment of the conduits therein by self-circulation of the treatment liquid therewithin, the further step of feeding of the treatment liquid from the economizer connected ahead of the steam generator directly to the superheater connected after the steam generator with said pump means while isolating said steam generator from said through-flow system, and including the subsequent step of renewing the treatment liquid in the steam generator by temporarily connecting same into through-flow system, wherein further treatment liquid from the pump and economizer is supplied to the steam generator and existing treatment liquid in the steam generator overflows to the following part of said through-flow system including said superheater. 